Authorization Adapter

Active Admin offers the ability to define and use your own authorization adapter. If implemented, the '#authorized?' will be called when an action is taken. By default, '#authorized?' returns true.

Setting up your own AuthorizationAdapter

Setting up your own AuthorizationAdapter is easy! The following example shows how to set up and tie your authorization adapter class to Active Admin:

# app/models/only_authors_authorization.rb
class OnlyAuthorsAuthorization < ActiveAdmin::AuthorizationAdapter

    def authorized?(action, subject = nil)
      case subject
      when normalized(Post)

        # Only let the author update and delete posts
        if action == :update || action == :destroy
          subject.author == user

        # If it's not an update or destroy, anyone can view it
        else
          true
        end

      else
        true
      end
    end

end

In order to hook up OnlyAuthorsAuthorization to Active Admin, go to your application's config/initializers/active_admin.rb and add/modify the line:

config.authorization_adapter = "OnlyAuthorsAuthorization"

Authorization adapters can be configured per ActiveAdmin namespace as well, for example:

ActiveAdmin.setup do |config|
  config.namespace :admin do |ns|
    ns.authorization_adapter = "AdminAuthorization"
  end
  config.namespace :my do |ns|
    ns.authorization_adapter = "DashboardAuthorization"
  end
end

Now, whenever a controller action is performed, the OnlyAuthorsAuthorization's #authorized? method will be called.

Getting Access to the Current User

From within your authorization adapter, you can call the #user method to retrieve the current user.

class OnlyAdmins < ActiveAdmin::AuthorizationAdapter

  def authorized?(action, subject = nil)
    user.admin?
  end

end

Scoping Collections in Authorization Adapters

ActiveAdmin::AuthorizationAdapter also provides a hook method (#scope_collection) for the adapter to scope the resource's collection. For example, you may want to centralize the scoping:

class OnlyMyAccount < ActiveAdmin::AuthorizationAdapter

  def authorized?(action, subject = nil)
    subject.account == user.account
  end

  def scope_collection(collection)
    collection.where(:account_id => user.account_id)
  end

end

All collections presented on Index Screens will be passed through this method and will be scoped accordingly.

Managing Access to Pages

Pages, just like resources, get authorized also. When authorization a page, the subject will be an instance of ActiveAdmin::Page.

class OnlyDashboard < ActiveAdmin::AuthorizationAdapter
  def authorized?(action, subject = nil)
    case subject
    when ActiveAdmin::Page
      if action == :read && subject.name == "Dashboard"
        true
      else
        false
      end
    else
      false
    end
  end
end

Action Types

By default Active Admin simplifies the controller actions into 4 actions:

• :read - This controls if the user can view the menu item as well as the index and show screens.
• :create - This controls if the user can view the new screen and submit the form to the create action.
• :update - This controls if the user can view the edit screen and submit the form to the update action.
• :destroy - This controls if the user can delete a resource.

Each of these actions is available as a constant. Eg: :read is available as ActiveAdmin::Authorization::READ.

Checking for Authorization in Controllers and Views

Active Admin provides a helper method to check if the current user is authorized to perform an action on a subject.

Simply use the `#authorized?(action, subject) method to check.

ActiveAdmin.register Post do

  index do
    column :title
    column "" do |post|
      if authorized?(:update, post)
        link_to("Edit", admin_post_path(post))
      end
    end

  end

end

If you are implementing a custom controller action, you can use the #authorize! method to raise an ActiveAdmin::AccessDenied exception.

ActiveAdmin.register Post do

  member_action :publish, :method => :post do
    post = Post.find(params[:id])

    authorize! :publish, post
    post.publish!

    flash[:notice] = "Post has been published"
    redirect_to [:admin, post]
  end

  action_item :only => :show do
    if !post.published? && authorized?(:publish, post)
      link_to("Publish", publish_admin_post_path(post), :method => :post)
    end
  end

end

Using the CanCan Adapter

Sub-classing ActiveAdmin::AuthorizationAdapter is fairly low level. Many times it's nicer to have a simpler DSL for managing authorization. Active Admin provides an adapter out of the box for CanCan.

To use the CanCan adapter, simply update the configuration in the Active Admin initializer:

config.authorization_adapter = ActiveAdmin::CanCanAdapter

By default this will use the ability class named "Ability". This can also be changed from the initializer:

config.cancan_ability_class = "MyCustomAbility"

Now you can simply use CanCan the way that you would expect and Active Admin will use it for authorization:

# app/models/ability.rb
class Ability
  include CanCan::Ability

  def initialize(user)
    can :manage, Post
    can :read, User
    can :manage, User, :id => user.id
    can :read, ActiveAdmin::Page, :name => "Dashboard"
  end

end

To view more details about the CanCan API, visit https://github.com/ryanb/cancan.